Comparison of the intracarotid amobarbital procedure and interictal cerebral 18-fluorodeoxyglucose positron emission tomography scans in refractory temporal lobe epilepsy.

The relationship between interictal focal hypometabolism determined by 18-fluorodeoxyglucose positron emission tomography (FDG-PET) scans and memory function with the intracarotid amobarbital procedure (IAP) was evaluated in 23 patients with temporal lobe epilepsy. All patients underwent prolonged EEG/video monitoring. The epileptogenic focus was defined by interictal epileptiform discharges and ictal onsets. All 23 patients had recorded seizures arising exclusively from one temporal lobe. PET showed temporal lobe hypometabolism ipsilateral to the epileptogenic focus in 86% (20 of 23) of patients; IAP showed impaired memory of the hemisphere of seizure onset in 65% (15 of 23). Sixty-five percent (13 of 20) of patients with focal hypometabolism had ipsilateral memory impairment. Memory impairment contralateral to the hypometabolic zone was not observed. Ninety-five percent (22 of 23) of patients demonstrated functional impairment by either PET or IAP (or both) on the epileptogenic side.     

FDG-PET and MRI in temporal lobe epilepsy: relationship to febrile seizures, hippocampal sclerosis and outcome

Objective – To correlate the volumetric head magnetic resonance imaging (MRI) and fluorodeoxyglucose-positron emission tomography (FDG-PET) scan findings with the history, intracarotid amobarbital procedure, pathology, and outcome in patients with medically refractory temporal lobe epilepsy. Material and methods – Thirty-eight patients with temporal lobe epilepsy treated surgically following a comprehensive presurgical evaluation. Follow-up ranged from 12 to 44 months. Results – Volumetric MRI showed ipsilateral hippocampal atrophy in 29 (76%), and PET scan showed ipsilateral temporal hypometabolism (PET-TH) in 31 (81.5%) of patients. Eighty-three percent of those patients with hippocampal sclerosis on MRI (MRI-HS) had ipsilateral PET-TH. Sixty-six percent of patients with MRI-HS had a history of prolonged febrile convulsions or a childhood febrile illness accompanied by convulsions, and 77% of patients with MRI-HS had pathologically proven hippocampal sclerosis (HS). Ninety percent became seizure free or had rare seizures. Conclusion – FDG-PET scans and head MRIs were complementary; 95% of patients had either MRI-HS or temporal hypometabolism. MRI-HS correlated with a history of febrile seizures and pathologically demonstrated hippocampal sclerosis. Ninety-three percent of patients had focal functional deficits on the epileptogenic side. Concordance between PET temporal hypometabolism and MRI-HS correlated with better outcome.     

Presurgical evaluation and surgical outcome of temporal lobe epilepsy

The authors analyzed 22 patients younger than 18 years of age with temporal lobe epilepsy (TLE) treated surgically. Patients underwent a comprehensive presurgical evaluation, including video-electroencephalogram. Fifty-five percent had a history of febrile seizures. Eighty-two percent had auraes and most exhibited oroalimentary and gestural automatisms. Contralateral dystonic posturing was present in 36% and postictal dysphasia in 54% of patients with left-sided resections. Cranial magnetic resonance imaging (MRI) was abnormal in 59% of patients. MRI revealed changes consistent with mesial temporal sclerosis in 8 (47%) of 17 patients without lesions. Fluorodeoxyglucose-positron emission tomography (PET) scans revealed ipsilateral temporal hypometabolism (PET-TH) in 12 (85.7%) of 14 patients. The intracarotid amobarbital procedure revealed impaired memory of the epileptogenic side in 59% of patients. Seventeen patients underwent en-bloc resections and five lesionectomies and resection of the epileptogenic area. There was no surgical morbidity or mortality. Forty-three percent had hippocampal sclerosis, 28.5% gliosis, 14% low-grade tumors, 9.5% cavernous angiomas, and 5% had no pathologic findings. Follow-up (6 months to 12 years) was available for 21 patients; 76% became seizure free, 19% had rare seizures, and 5% had a worthwhile improvement. TLE can be safely treated surgically in younger patients with excellent results. The clinical manifestations were similar to adult patients. PET-TH was present even at a younger age, suggesting that the focal functional deficits appear early in patients with medically refractory TLE, which may help in the early identification of these patients.     

Magnetic resonance imaging in intractable partial epilepsy: correlative studies

A study was performed evaluating magnetic resonance imaging (MRI) in 35 patients with intractable complex partial seizures in whom computed tomographic (CT) scans showed no focal abnormalities. These results were correlated with positron emission tomography evaluation (PET), the electroencephalographic ictal onset, and findings during pathological examination. Seven patients had structural lesions that were epileptogenic, detected by MRI; the lesions were tuberous sclerosis, astrocytomas, or hamartomas. Three of these 7 patients underwent PET scanning, which was normal in all. Of 18 patients with mesial temporal sclerosis, 10 were shown by PET to have temporal lobe hypometabolism, though all 18 had normal MRI findings. The results indicate that MRI contributes information to that provided by CT and PET, by detecting nonsclerotic epileptogenic lesions of the temporal lobe.     

Is 11C-flumazenil PET superior to 18FDG PET and 123I-iomazenil SPECT in presurgical evaluation of temporal lobe epilepsy?

OBJECTIVE: To determine the contribution of 18FDG PET, 11C-flumazenil PET, and 123I-iomazenil SPECT to the presurgical evaluation of patients with medically intractable complex partial seizures. METHODS: Presurgical evaluation was performed in 23 patients, who were considered candidates for temporal lobe resective surgery (14 females and nine males with a median age of 34 (range 13 to 50) years). The presurgical diagnosis was based on seizure semiology as demonstrated with ictal video recording, ictal and interictal scalp EEG recordings, and MRI. RESULTS: Eighteen patients had convergent findings in clinical semiology, interictal and ictal EEG with scalp and sphenoidal electrodes, and MRI that warranted surgery without depth EEG (DEEG). In five patients with insufficient precision of localisation, DEEG with intracerebral and subdural electrodes was performed. MRI showed abnormalities in 22 out of 23 patients. Of these 22, 18 had mesial temporal sclerosis. This was limited to the mesial temporal lobe in four and more widespread in the temporal lobe in 14 patients. In one patient only enlargement of the temporal horn was found and in three others only white matter lesions were detected. 18FDG PET showed a large area of glucose hypometabolism in the epileptogenic temporal lobe, with an extension outside the temporal lobe in 10 of 23 patients. Only in one of these patients DEEG showed extratemporal abnormalities that were concordant with a significant extratemporal extension of hypometabolism in 18FDG PET. 18FDG PET was compared with the results of scalp EEG: in none of the patients was an anterior temporal ictal onset in scalp EEG related to a maximum hypometabolism in the mesial temporal area. By contrast, the region of abnormality indicated by 11C-flumazenil PET was much more restricted, also when compared with DEEG findings. Extension of abnormality outside the lobe of surgery was seen in only two patients with 11C-flumazenil and was less pronounced compared with the intratemporal abnormality. Both 18FDG PET and 11C-flumazenil PET reliably indicated the epileptogenic temporal lobe. Thus these techniques provide valuable support for the presurgical diagnosis, especially in patients with non-lesional MRI or non-lateralising or localising scalp EEG recordings. In those patients in whom phase 1 presurgical evaluation on the basis of classic methods does not allow a localisation of the epileptogenic area, PET studies may provide valuable information for the strategy of the implantation of intracranial electrodes for DEEG. Previous studies have suggested that 11C-flumazenil binding has a closer spatial relationship with the zone of ictal onset than the area of glucose hypometabolism, but this study suggests rather that the decrease in the 11C-flumazenil binding simply reflects a loss of neurons expressing the benzodiazepine-GABA receptor. 11C-flumazenil PET did not prove to be superior to 18FDG PET. CONCLUSION: In 21 patients sufficient material was obtained at surgery for a pathological examination. In 17 mesial temporal sclerosis, in one an oligodendroglioma grade B, in another a vascular malformation and in two patients no abnormalities were found. Although all 21 patients with pathological abnormality showed hypometabolic zones with 18FDG PET and a decreased uptake in 11C-flumazenil binding, there was no strong correlation between pathological diagnosis and functional abnormal areas in PET. Grading of medial temporal sclerosis according to the Wyler criteria showed no correlation with the degree of hypometabolism in either 18FDG or 11C-flumazenil PET. The interictal 123I-iomazenil SPECT technique was highly inaccurate in localising the lobe of surgery.     

Temporal lobe epilepsy: analysis of patients with dual pathology

OBJECTIVES: To determine the frequency and types of dual pathology in patients with temporal lobe epilepsy (TLE) and to analyze the clinical manifestations and surgical outcome. MATERIAL AND METHODS: A total of 240 patients with TLE underwent temporal resections following a comprehensive pre-surgical evaluation. Thirty-seven (15.4%) of these had hippocampal sclerosis (HS) or temporal lobe gliosis in association with another lesion (dual pathology). RESULTS: Eighteen of 37 patients with dual pathology had heterotopia of the temporal lobe, nine had cortical dysplasia, four had cavernous angiomas or arteriovenous malformations, one had a dysembryoplastic neuroepithelial tumor, one had a contusion and four patients had cerebral infarctions in childhood. 68.5% had abnormal head magnetic resonance imagings, 91.3% had abnormal positron emission tomography scans, and 96% had abnormal ictal SPECT. The intracarotid amobarbital procedure (IAP) showed impaired memory of the epileptogenic side in 72% of the patients. Twenty patients had left and 17 had right-sided en bloc temporal resections, including the lesion and mesial temporal structures. Twenty-six (70.2%) became seizure-free, eight (21.6%) had rare seizures, two (5.4%) had worthwhile seizure reduction and one (2.7%) had no improvement (range of follow-up 1-16 years, mean = 7.4 years). CONCLUSIONS: 15.4% had dual pathology. The dual pathology was almost exclusively seen in patients whose lesions were congenital, or occurred early in life, suggesting that the hippocampus is more vulnerable and more readily develops HS in early childhood. Resections, including the lateral and mesial temporal structures led to a favorable outcome with no mortality and little morbidity.     

Unitemporal vs bitemporal hypometabolism in mesial temporal lobe epilepsy

BACKGROUND: Patients with mesial temporal lobe epilepsy (TLE) often show bilateral temporal hypometabolism (BTH), but the nature of this finding has not been well established. OBJECTIVE: To compare the clinical characteristics between unitemporal hypometabolism (UTH) and BTH patients in mesial TLE. DESIGN: Cross-sectional study. SETTING: Epilepsy center at university hospital in Seoul, Korea. PATIENTS: We enrolled 95 patients with mesial TLE, 87 of whom had subsequently undergone surgery. Seizures, interictal and ictal electroencephalography (EEG), brain magnetic resonance imaging, Wada test, and neuropsychological test results were reviewed. (18)F-fluorodeoxyglucose positron emission tomography scans were interpreted visually. Patients were divided into 2 groups: UTH and BTH. RESULTS: There were 59 UTH patients and 36 BTH patients. Semiologic analysis showed that UTH patients had higher frequencies of aura and unilateral dystonic posturing, whereas BTH patients had higher frequencies of a nonlateralized bilateral ictal EEG pattern and bilateral interictal spikes. Moreover, BTH patients had more frequent symmetric Wada memory scores and white matter changes in the bilateral temporal lobes on brain magnetic resonance imaging than UTH patients. All UTH patients with bilateral TLE on scalp EEG showed unilateral seizure onset on intracranial EEG. CONCLUSIONS: The characteristic clinical findings of mesial TLE with BTH were a more frequent nonlateralized ictal EEG pattern, bitemporal interictal spikes, symmetric Wada memory score, and the anterior temporal white matter changes, and less frequent aura and unilateral dystonic posturing. Surgical outcomes were similar and good in both groups, although surgery could not be performed in 8 BTH patients (22%).     

Temporal lobe epilepsy with bilateral seizure origin studied by [18F]FDG-positron emission tomography

Nine patients who underwent presurgical evaluation because of medically refractory temporal lobe epilepsy (TLE) showed either unilateral, although alternating in side, or bilateral simultaneous seizure onsets in both temporal lobes (TL). EEG recordings with semi-invasive foramen ovale electrodes revealed in seven patients a predominance of seizure onset in one TL of between 50% and 88%. In two patients the majority of seizures originated simultaneously in both TL. In four patients a unilateral selective amygdalohippocampectomy resulted in a good to excellent seizure outcome without noteworthy memory deficits and confirmed the preoperative lateralization of the primary epileptogenic focus by interictal ¹⁸F-fluorodeoxyglucose positron emission tomography (PET). Five patients were rejected from surgery due to strong bilaterality of their epilepsy and/or divergent presurgical findings. PET contributed to the decision of whether surgery should be performed: all patients who underwent surgery had a unilateral TL hypometabolism which was concordant with the findings of other tests. Patients in whom surgery was denied had either bilateral temporal hypometabolism or the PET findings were discordant with other results obtained during the presurgical evaluation.     

What is needed for resective epilepsy surgery from a neurosurgical point of view?

Invasive versus non-invasive epileptogenic zone definition was analyzed in a series of 89 patients operated on for drug-resistant epilepsy. In the group of 69 cortical resections, 26% needed invasive recordings, 13.5% when foreign-tissue lesions had been detected by MRI and 32% when were absent. In this last group temporal resections had invasive EEG recordings in 23.5% versus 54.5% when the epileptogenic zone was extratemporal. In a group of 43 temporal resections with more than one year follow-up MRI has detected some abnormality in 84%. Excluding focal lesions, MRI detected hippocampal/temporal lobe atrophy in 66% of the cases in agreement with other noninvasive tests and in 4% contralateral to the epileptogenic zone located by subdural strips. The outcome analysis showed that 85% of the patients with MRI-EEG agreement were seizure free in contrast to only 43% when MRI was non-lateralizing. Future studies has to be oriented to better understand the epileptic process of patients without MRI abnormalities.     

Longitudinal changes in cortical glucose hypometabolism in children with intractable epilepsy

In children with partial epilepsy, there is increasing evidence to suggest that not all cortical regions showing glucose hypometabolism on positron emission tomography (PET) represent epileptogenic cortex but that some hypometabolic areas might be the result of repeated seizures. Most of the supportive data, however, have come from cross-sectional imaging studies. To evaluate longitudinal changes in cortical glucose hypometabolism, we compared two sequential [(18)F]fluorodeoxyglucose (FDG) PET scans performed 7 to 44 months apart in 15 children with intractable nonlesional partial epilepsy. The extent of hypometabolic cortex on the side of the electroencephalography-verified epileptic focus and its changes between the two PET scans were measured and correlated to clinical seizure variables. The change in seizure frequency between the two PET scans correlated positively with the change in the extent of cortical glucose hypometabolism (r = .8, P <.001). Most patients with persistent or increased seizure frequency (one or more seizures per day) showed enlargement in the area of hypometabolic cortex on the second PET scan. In contrast, patients whose seizure frequency had decreased below daily seizures between the first and second PET scans showed a decrease in the size of the hypometabolic cortex. These results support the notion that the extent of cortical glucose hypometabolism on PET scanning can undergo dynamic changes, and these are, at least partly, related to the frequency of seizures. The findings have implications on how aggressively persistent seizures should be treated in children. (J Child Neurol 2006;21:26-31).     

Surgical outcome in PET-positive, MRI-negative patients with temporal lobe epilepsy

Purpose: Fluorodeoxyglucose positron emission computed tomography (FDG‐PET) hypometabolism is important for surgical planning in patients with temporal lobe epilepsy (TLE), but its significance remains unclear in patients who do not have evidence of mesial temporal sclerosis (MTS) on magnetic resonance imaging (MRI). We examined surgical outcomes in a group of PET‐positive, MRI‐negative patients and compared them with those of patients with MTS. Methods: We queried the Thomas Jefferson University Surgical Epilepsy Database for patients who underwent anterior temporal lobectomy (ATL) from 1991 to 2009 and who had unilateral temporal PET hypometabolism without an epileptogenic lesion on MRI (PET+/MRI?). We compared this group to the group of patients who underwent ATL and who had MTS on MRI. Patients with discordant ictal electroencephalography (EEG) were excluded. Surgical outcomes were compared using percentages of Engel class I outcomes at 2 and 5 years as well as Kaplan‐Meier survival statistic, with time to seizure recurrence as survival time. A subgroup of PET+/MRI? patients who underwent surgical implantation prior to resection was compared to PET+/MRI? patients who went directly to resection without implantation. Key Findings: There were 46 PET+/MRI? patients (of whom 36 had 2‐year surgical outcome available) and 147 MTS patients. There was no difference between the two groups with regard to history of febrile convulsions, generalized tonic–clonic seizures, interictal spikes, depression, or family history. Mean age at first seizure was higher in PET+/MRI? patients (19 ± 13 vs.14 ± 13 years, Mann‐Whitney test, p = 0.008) and disease duration was shorter (14 ± 10 vs. 22 ± 13 years, student’s t‐test, p = 0.0006). Class I surgical outcomes did not differ significantly between the PET+/MRI? patients and the MTS group (2 and 5 year outcomes were 76% and 75% for the PET+/MRI? group, and 71% and 78% for the MTS group); neither did outcomes of the PET+/MRI? patients who were implanted prior to resection versus those who went directly to surgery (implanted patients had 71% and 67% class I outcomes at 2 and 5 years, whereas. nonimplanted patients had 77% and 78% class I outcomes, p = 0.66 and 0.28). Kaplan‐Meier survival statistics for both comparisons were nonsignificant at 5 years. Dentate gyrus and hilar cell counts obtained from pathology for a sample of patients also did not differ between groups. Significance: PET‐positive, MRI‐negative TLE patients in our study had excellent surgical outcomes after ATL, very similar to those in patients with MTS, regardless of whether or not they undergo intracranial monitoring. These patients should be considered prime candidates for ATL, and intracranial monitoring is probably unnecessary in the absence of discordant data.     

发作间期PET和MR海马像在难治性颞叶癫癇术前定侧中的应用

目的 探讨发作间期18FDG-PET和MR海马像在难治性颞叶癫(?)（TLE）致(?)源术前定侧中的价值。方法 对17例药物难治性TLE患者术前定侧资料及术后随诊情况进行分析。结果 本组患者中,有12例（71％）患者MR显示海马硬化（HS）,海马萎缩与信号改变常共存,T2加权像和FLAIR序列有利于显示信号的改变。HS侧多提示为致(?)源侧。PET检查均显示有至少一侧颞叶低代谢改变,并常多发或范围弥散。PET与MR的定侧准确率分别是100％（13/13）、77％（10/13）,经x2检验两者间无差异（P>0.05）。结论　18FDG-PET和MR海马像在致(?)源定侧中的作用是互补的,当颞叶低代谢侧与海马硬化侧相一致时手术效果较好。     

Neocortical temporal FDG-PET hypometabolism correlates with temporal lobe atrophy in hippocampal sclerosis associated with microscopic cortical dysplasia

PURPOSE: Medically intractable temporal lobe epilepsy (TLE) due to hippocampal sclerosis (HS), with or without cortical dysplasia (CD), is associated with atrophy of the hippocampal formation and regional fluorodeoxyglucose positron-emission tomography (FDG-PET) hypometabolism. The relation between areas of functional and structural abnormalities is not well understood. We investigate the relation between FDG-PET metabolism and temporal lobe (TL) and hippocampal atrophy in patients with histologically proven isolated HS and HS associated with CD. METHODS: Twenty-three patients underwent en bloc resection of the mesial and anterolateral neocortical structures. Ten patients were diagnosed with isolated HS; 13 patients had associated microscopic CD. Temporal lobe volumes (TLVs) and hippocampal volumes were measured. Magnetic resonance imaging (MRI) and PET were co-registered, and regions of interest (ROIs) determined as gray matter of the mesial, lateral, and anterior temporal lobe. RESULTS: All patients (HS with or without CD) had significant ipsilateral PET hypometabolism in all three regions studied (p < 0.0001). In patients with isolated HS, the most prominent hypometabolism was in the anterior and mesial temporal lobe, whereas in dual pathology, it was in the lateral temporal lobe. TLVs and hippocampal volumes were significantly smaller on the epileptogenic side (p < 0.05). The PET asymmetries ipsilateral/contralateral to the epileptogenic zone and TLV asymmetries correlated significantly for the anterior and lateral temporal lobes (p < 0.05) in the HS+CD group, but not in the isolated HS group. Mesial temporal hypometabolism was not significantly different between the two groups. CONCLUSIONS: Temporal neocortical microscopic CD with concurrent HS is associated with more prominent lateral temporal metabolic dysfunction compared with isolated HS in TL atrophy. Further studies are needed to confirm these findings and correlate the PET hypometabolic patterns with outcome data in patients operated on for HS with or without CD.     

Longitudinal Follow-Up in 145 Patients with Medically Refractory Temporal Lobe Epilepsy Treated Surgically Between 1984 and 1995

PURPOSE: There are few studies of prolonged longitudinal follow-up after temporal resections. METHODS: We analyzed 145 consecutive patients with temporal lobe epilepsy treated surgically. Patients had a comprehensive presurgical evaluation, including video-EEG, psychometric testing, magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT), intracarotid amobarbital procedure (IAP), and recently, volumetric head MRIs and F-fluorodeoxyglucose-positron emission tomography (FDG-PET) scans. Most had en bloc temporal resections, and a few had lesionectomies and resection of the epileptogenic zone. There was no surgical mortality. Longitudinal follow-up data of the seizure outcome were analyzed by actuarial analysis. Patients were followed up at 6 weeks, 3 months, 6 months, and then on a yearly basis. The mean follow-up was 5.6 years. RESULTS: Sixty-six percent were seizure free at 1 year, 63% at 2 years, 60% at 5 years, and 55% at 10 years follow-up. Moreover, 85%, became seizure free for > or =2 at the time of last follow-up or had rare seizures. Patients who were seizure free for 1 and 2 years after surgery, had an 83% and 92% probability, respectively, of remaining seizure free at the time of last follow-up. Ninety-one percent of patients with small tumors and cavernous angiomas became seizure free compared with 69% of patients with hippocampal sclerosis. CONCLUSIONS: Actuarial analysis showed that the long-term surgical outcome of temporal lobe epilepsy remains favorable. Follow-up at 1 and 2 years is highly predictive of the long-term outcome. Patients with discrete lesions had the best outcome. Most of the patients with late recurrences had hippocampal sclerosis or temporal lobe gliosis. Some patients with postoperative seizures eventually became seizure free, reflecting the running-down phenomenon.     

False Lateralization of Temporal Lobe Epilepsy with FDG Positron Emission Tomography

Summary: We report 2 patients in whom visual interpretation of interictal positron emission tomography (PET) with [¹⁸F]fluorodeoxyglucose (FDG) suggested false lateralization of an epileptic focus. PET scans were interpreted as showing diffuse left temporal lobe hypometabolism in 1 patient and lateral temporal hypometabolism in the other. However, seizures began in the right mesial temporal lobe in both patients, and both responded favorably to right temporal lobectomy. In 1 patient, the intra-cranial EEG showed continuous asymptomatic subclinical seizure activity emanating from the right amygdala. These limbic discharges probably caused unrecognized right temporal lobe hypermetabolism. In the other case, quantitative analysis of metabolic rates showed conflicting mesial and lateral metabolic indexes. Frequent mesial interictal discharges might have increased lateral temporal metabolism. We conclude that asymptomatic epileptiform activity may alter temporal lobe metabolism and that quantitative PET analysis helps clarify contradictory visual PET interpretations.     

18F-FCWAY and 18F-FDG PET in MRI-negative temporal lobe epilepsy

Background: Positron emission tomography (PET) with ¹⁸F‐fluorodeoxyglucose (FDG) shows widespread hypometabolism even in temporal lobe epilepsy (TLE) patients with mesial temporal foci. ¹⁸F‐trans‐4‐fluoro‐N‐2‐[4‐(2‐methoxyphenyl) piperazin‐1‐yl]ethyl‐N‐(2‐pyridyl)cyclohexane carboxamide (¹⁸F‐FCWAY) PET may show more specific 5‐HT_1A‐receptor binding reduction in seizure initiation than in propagation regions. ¹⁸FCWAY PET might be valuable for detecting epileptic foci, and distinguishing mesial from lateral temporal foci in MRI‐negative patients with TLE. Methods: We performed ¹⁸F‐FCWAY‐PET and ¹⁸F‐FDG‐PET in 12 MRI‐negative TLE patients who had had either surgery or subdural electrode recording, and 15 healthy volunteers. After partial volume correction for brain atrophy, free fraction‐corrected volume of distribution (V/f1) measurement and asymmetry indices (AIs) were computed. We compared ¹⁸F‐FCWAY‐PET and ¹⁸F‐FDG‐PET results with scalp video electroencephalography (EEG), invasive EEG, and surgical outcome. Results: Mean ¹⁸F‐FCWAY V/f1, compared with normal controls, was decreased significantly in fusiform gyrus, hippocampus, and parahippocampus ipsilateral to epileptic foci, and AIs were significantly greater in hippocampus, parahippocampus, fusiform gyrus, amygdala, and inferior temporal regions. Eleven patients had clearly lateralized epileptogenic zones. Nine had congruent, and two nonlateralized, ¹⁸F‐FCWAY PET. One patient with bitemporal seizure onset had nonlateralized ¹⁸F‐FCWAY‐PET. ¹⁸F‐FDG‐PET showed congruent hypometabolism in 7 of 11 EEG‐lateralized patients, bilateral hypometabolic regions in one, contralateral hypometabolism in one, as well as lateralized hypometabolism in the patient with bitemporal subdural seizure onset. Patients with mesial temporal foci tended to have lower superior and midtemporal ¹⁸F‐FCWAY V/f1 binding AI than those with lateral or diffuse foci. Conclusion: ¹⁸F‐FCWAY‐PET can detect reduced binding in patients with normal MRI, and may be more accurate than ¹⁸F‐FDG‐PET.     

Correlation of Hippocampal Neuronal Density and FDG-PET in Mesial Temporal Lobe Epilepsy

Summary: Purpose: Interictal [¹⁸F]fluorodeoxyglucose (FDG) positron emission tomography (PET) reveals regional hypometabolism in 60–80% of patients with mesial temporal lobe epilepsy (MTLE). The extent of hypometabolism generally extends beyond the epileptogenic zone. The pathophysiology underlying this widespread change is unknown. This study evaluated the relation between hippocampal neuronal loss and hypometabolism in patients with MTLE.
Methods: Forty-three patients with MTLE after anterior temporal lobectomy were included. Pathology demonstrated mesial temporal sclerosis (n = 41) or endfolium sclerosis (n = 2). Interictal FDG-PET scans were graded by visual analysis on a scale ranging from normal (grade 1) to severe (grade 5) hypometabolism. Neuronal counting was performed in the subiculum, hippocampal subfields, and dentate granular cell layer (DG). Neuronal density of patients was compared with that of seven autopsy controls. Data were compared by using Student's t tests and Kruskal-Wallis one-way analysis of variance (ANOVA).
Results: Significant neuronal loss in CA1 through CA4 and DG was found in patients compared with controls. Neuronal density in the subiculum, CA1, CA4, and DG did not correlate with severity of hypometabolism. However, patients with abnormal FDG-PET had higher neuronal density in CA2 and CA3 versus patients with normal studies.
Conclusions: This study supports a previous observation that degree of FDG-PET hypometabolism does not parallel severity of hippocampal neuronal loss in MTLE.     

Factors contributing to clinical seizure lateralization in patients with mesial temporal lobe epilepsy

Clinical seizure semiology can provide important information on the lateralization of the epileptogenic zone. We investigated factors associated with clinical seizure lateralization in patients with pathologically proven mesial temporal sclerosis. We reviewed 243 seizures of 58 patients. Clinical lateralization was possible in 155 (63.8%) of 243 seizures. Lateralization was correct in 144 (92.9%) of 155 lateralized seizures. Logistic regression analysis showed that age at onset (p = 0.001; odds ra tio = 1.089, 95% confidence interval = 1.035-1.145) and the contralateral propagation pattern of ictal discharges (p = 0.001; odds ratio = 3.544, 95% confidence interval = 1.723-7.289) correlated with clinical seizure lateralization. The patient group with clinically lateralized seizures had a younger age at onset of habitual seizures compared to the clinically nonlateralized group (11.1 +/- 6.3 vs. 15.6 +/- 8.4 years; p < 0.001). Of seizures without bitemporal asynchrony or switch of lateralization, 70.7% were clinically lateralized compared with only 46.4% of seizures with asynchrony or lateralization switch. The present results suggest that the age of epilepsy onset and the ictal scalp EEG propagation pattern affect clinical seizure lateralization in patients with mesial temporal sclerosis.     

Seizure outcome after epilepsy surgery in patients with normal preoperative MRI

OBJECTIVE: To determine outcome after epilepsy surgery in patients with normal preoperative magnetic resonance imaging (MRI). METHODS: 24 adult and paediatric patients with normal preoperative MRIs were studied. They underwent epilepsy surgery between 1994 and 2001 and had at least one year of follow up. RESULTS: At the most recent follow up, nine patients (37%) were seizure-free and 18 (75%) had at least a 90% reduction in seizure frequency with weekly or monthly seizures. Seizure freedom was not significantly different after resections in frontal (5/9) or temporal regions (4/13) (p = 0.24, Fisher's exact test), or among patients with or without localising features on EEG, PET, or ictal SPECT. Subdural grids, used in 15 of 24 patients, helped tailor resections but were not associated with differences in outcome. Histopathology showed cortical dysplasia in 10 patients (42%), non-specific findings in 13 (54%), and hippocampal sclerosis in one (4%). Cortical dysplasia was seen in seven patients with frontal resection (78%) and non-specific findings in nine (69%) with temporal resection. Seizure outcome did not differ on the basis of location of resection or histopathology. CONCLUSIONS: While these results were less favourable than expected for patients with focal epileptogenic lesions seen on MRI, they represented worthwhile improvement for this patient population with high preoperative seizure burden. In this highly selected group, no single test or combination of tests further predicted postoperative seizure outcome.     

Presurgical evaluation for partial epilepsy: relative contributions of chronic depth-electrode recordings versus FDG-PET and scalp-sphenoidal ictal EEG

One hundred fifty-three patients with medically refractory partial epilepsy underwent chronic stereotactic depth-electrode EEG (SEEG) evaluations after being studied by positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) and scalp-sphenoidal EEG telemetry. We carried out retrospective standardized reviews of local cerebral metabolism and scalp-sphenoidal ictal onsets to determine when SEEG recordings revealed additional useful information. FDG-PET localization was misleading in only 3 patients with temporal lobe SEEG ictal onsets for whom extratemporal or contralateral hypometabolism could be attributed to obvious nonepileptic structural defects. Two patients with predominantly temporal hypometabolism may have had frontal epileptogenic regions, but ultimate localization remains uncertain. Scalp-sphenoidal ictal onsets were misleading in 5 patients. For 37 patients with congruent focal scalp-sphenoidal ictal onsets and temporal hypometabolic zones, SEEG recordings never demonstrated extratemporal or contralateral epileptogenic regions; however, 3 of these patients had nondiagnostic SEEG evaluations. The results of subsequent subdural grid recordings indicated that at least 1 of these patients may have been denied beneficial surgery as a result of an equivocal SEEG evaluation. Weighing risks and benefits, it is concluded that anterior temporal lobectomy is justified without chronic intracranial recording when specific criteria for focal scalp-sphenoidal ictal EEG onsets are met, localized hypometabolism predominantly involves the same temporal lobe, and no other conflicting information has been obtained from additional tests of focal functional deficit, structural imaging, or seizure semiology.